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24 On the disappearance of the Ice on Lake Charnplaht. 



but I have not hitherto examined where the depth has exceeded 

 35 feet; I should have attempted it this spring but for the un- 

 expected disappearance of the ice, the Fast of March.^ ' 



A few days after the disappearance of the ice this year, I found 

 the temperature of the water to be 36 J^^ and, as the lake was at 

 the time much agitated by the wind, this was, doubtless, very 

 nearly the mean temperature ofnhe whole mass of water. 



There are three well attested facts connected with this subject, 

 M^hich, taken together, appear to me to afford a full and satisfac- 

 tory explanation of the phenomenon. 



1. The great body of ice is previously always reduced to the 

 honei/'Comb stviicwre^ in which condition any considerable agita- 

 tion of the water causes it to separate into minute divisions- 



2. The temperature of the great mass of water is always several 

 degrees above the freezing point, and in a condition to dissolve 

 the minute divisions of ice with great facility when agitated in it. 



3. The phenomenon is always attended by a very high wind, 

 producing the agitation required. 



In addition to theoretic objections to the opinion that the ice 

 sinks when it disappears suddenlyj we, who liv^e on the shores of 

 the lake, think we have ocular proof that it does not take place- 

 We see the ice, while yet spreading over the whole surface of the 

 lake, gradually wasting as the spring advances, and becoming less 

 firm, till at length it is so far disintegrated that a stick may be 

 easily thrust through it, while it is still from six to twelve inches 

 thick. This disintegration is often carried so far, before the gen- 

 eral icy covering is disturbed, that the ice has little more solidity 

 or tenacity than loose snow saturated with water. In this state 

 of things a strong wind soon produces rents in the ice, the waters, 

 before pent up and quiet, are thrown into violent agitation, and 

 we actually see the slightly cohering masses falling to pieces and 

 dissolving at the surface of the lake; but we never see the ice 

 sinking, rior^an I learn that any evidence of this has ever been 

 observed in masses lying at the bottom of the lake. 



The objection to this hypothesis — "that so sudden and exten- 

 sive a conversion of a solid into a fluid, as it supposes, would pro- 

 duce a sudden and violent frost through the neighboring coun- 

 try," — would, undoubtedly, have weight were the caloric required 



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* Although the lake this year be^n to open, in some place?, before the middle of 

 March, it renuiiued mostly covered with ice of considerable thickness and firmness 

 till the 29th of that month, -uhen, in the afternoon, a brisk -wind sprang up from the 

 south, which increased to a stron*^ gale during the ui^ht, and continued to blow with 

 great violence in the same direction during the ^Oth and np to noon on the 31st, 

 TPhen it clmnged to the west and blew a strong gal^n that -direction tlirough the re- 

 mainder of the day. Before evening on the SOth, the ice had all vanished from 

 the broader parts of the lake, and on the 1st day of April, the lafce and bays, so 

 far as visible from this place, were entirely cleared,«f ice, Thisl^onsidering the 

 thickness and firmness of the ice at the time, is one of the most remarkable clear- 

 ances of the lak%we have witnessed for several yeara. 



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